APPROVAL

The enzyme acetolactate synthase (ALS, EC 4.1.3.18) is the site of action of the herbicide chlorsulfuron (2-chloro-N-[(4-methoxy-6-methyl-l,3,5,-triazin-2yl)aminocarbonyl]benzenesulfonamide). This enzyme was extracted from plant material and immobilized in a cartridge packed with a silica based activated affinity media. The activity of the immobilized enzyme was inhibited by nanomolar concentrations of chlorsulfuron. A 60 % recovery of radio-labeled chlorsulfuron from treated soil was demonstrated. Analytical standards of chiorsulfuron recovered from soil inhibited immobilized ALS to a greater degree at higher herbicide concentrations. Results indicate this technique is capable of chlorsulfuron detection down to about 1 ppb (1.12 g/ha). This technique, therefore, represents a method with the potential to be faster and more economical than the present method which uses high performance liquid chromatography